Enhanced oil recovery process using water soluble polymers having improved shear resistance

Abstract

An enhanced oil recovery process using high molecular weight water soluble polymer consisting in: —dispersing said polymer in injection brine, —and then injecting the dispersed polymer in the subterranean formation, characterized in that the high molecular weight water soluble polymer contains at least a non-ionic monomer and at least an amphiphilic monomer containing at least a side chain having an HLB above 4.5, said high molecular weight water soluble polymer having a molecular weight of more than 10 000 000.

1 . An enhanced oil recovery process using high molecular weight water soluble polymer consisting in:
 dispersing said polymer in injection brine,   and then injecting the dispersed polymer in the subterranean formation, characterized in that the high molecular weight water soluble polymer contains at least a non-ionic monomer and at least an amphiphilic monomer containing at least a side chain having an HLB above 4.5, said high molecular weight water soluble polymer having a molecular weight of more than 10 000 000.   
     
     
         2 . An enhanced oil recovery process according to  claim 1 , characterized in that the amphiphilic monomer represents less that 10% by weight of the high molecular weight water soluble polymer, preferably between 0.1% and 7%, more preferably between 0.2% and 5%. 
     
     
         3 . An enhanced oil recovery process according to  claim 1 , characterized in that the non-ionic monomer is selected from the group containing acrylamide, methacrylamide, N-vinyl pyrrolidone, N-vinyl formamide, N,N dimethylacrylamide, N-vinyl acetamide, N-vinylpyridine, N-vinylimidazole, isopropyl acrylamide and polyethelene glycol methacrylate. 
     
     
         4 . An enhanced oil recovery process according to  claim 1 , characterized in that the amphiphilic monomer is selected from the group comprising (meth)acrylamide, (meth)acrylic, vinyl, allyl or maleic backbone, having a side group selected from the group of alkyl, arylalkyl containing at least one heteroatom. 
     
     
         5 . An enhanced oil recovery process according to  claim 1 , characterized in that the amphiphilic monomer is selected from the group containing acrylamido undecanoic acid, acrylamido methyl undodecyl sulphonic acid, dimethyl dodecyl propyl methacrylamide ammonium chloride, behenyl 25-ethoxylated methacrylate. 
     
     
         6 . An enhanced oil recovery process according to  claim 1 , characterized in that the high molecular weight water soluble polymer comprises at least one anionic monomer(s) selected from the group comprising, acrylic acid, methacrylic acid and salts thereof, 2-acrylamido-2-methylpropane sulphonic acid (ATBS) and salts thereof. 
     
     
         7 . An enhanced oil recovery process according to  claim 1 , characterized in that the high molecular weight water soluble polymer has a molecular weight from 11.000.000 to 35.000.000. 
     
     
         8 . An enhanced oil recovery process according to  claim 1 , characterized in that the high molecular weight water soluble polymer is obtained by inverse emulsion or water in water polymerisation. 
     
     
         9 . An enhanced oil recovery process according to  claim 1 , wherein the high molecular weight water soluble polymer is injected at a rate of 200 to 7500 ppm.